Fluxgate magnetic sensors are used in a variety of applications to produce a corresponding output signal representing a detected magnetic field, for example, for current sensors, electronic compass or digital magnetometer devices, and position sensing applications. Fluxgate devices are constructed using a magnetic core with excitation and sense windings or coils, with the excitation coil being driven with a bidirectional signal and the sense coil providing an output signal which can be integrated to determine the external magnetic field strength. Several different approaches have been commonly used for interfacing fluxgate sense coils with external circuitry in order to provide an output voltage signal or digital value representing the detected external magnetic field. Many conventional sensor readout circuits amplify the output voltage and obtain an average value through filtering, and certain approaches employ a delta-sigma modulator and integrator for producing a sensor output. Certain proposed designs use sample and hold circuits or nonlinear averaging circuitry known as box-car circuits requiring precise timing control to store the voltages on capacitors of the individual boxcar circuits, with an adder to measure the voltage equivalent representing the maximum of the induced signal in the sense coil over a series of steps. Other fluxgate sensor readout circuits use rectifiers with low pass filters in which the signal is filtered and thus averaged through a full excitation cycle or period in order to produce a rectified voltage signal proportional to the measured magnetic field. However, these conventional approaches require significant amounts of circuitry and therefore occupy valuable space on an integrated circuit, and averaging through a full excitation cycle lowers the effective gain. Accordingly there is a continuing need for improved sensor readout apparatus for fluxgate magnetic sensors to provide output signals indicating a detected magnetic field while occupying minimal integrated circuit area without consuming excessive power.